Wireless communication systems are widely used to provide voice and data services for multiple users using a variety of access terminals such as cellular telephones, laptop computers and various multimedia devices. Such communications systems can encompass local area networks, such as IEEE 801.11 networks, cellular telephone and/or mobile broadband networks. The communication system can use one or more multiple access techniques, such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA) and others. Mobile broadband networks can conform to a number of standards such as the main 2nd-Generation (2G) technology Global System for Mobile Communications (GSM), the main 3rd-Generation (3G) technology Universal Mobile Telecommunications System (UMTS) and the main 4th-Generation (4G) technology Long Term Evolution (LTE).
A wireless network may include a wireless device and a plurality of base stations. The wireless device may be a notebook computer, a mobile phone or a Personal Digital Assistant (PDA), a media player, a gaming device or the like. The base stations communicate with the wireless device over a plurality of wireless channels coupled between the wireless device and the base stations (e.g., a downlink channel from a base station to a wireless device). The wireless device may send back information, including channel information, to the base stations over a plurality of reverse channels (e.g., an uplink channel from the wireless device to the base station or a backhaul link between base stations or relay nodes).
The wireless device may include a processor, a transmitter and a receiver. The transmitter may be coupled to one transmit antenna. The receiver may be coupled to a receive antenna. Alternatively, both the transmitter and the receiver are coupled to the same antenna via a duplexer. One major function of the receiver is rejecting unwanted noise such as additive thermal noise and multiplicative phase noise so that a desired signal from a wide spectrum of signals can be recovered.
Unwanted noise may prevent the receiver from correctly recovering a signal. For example, phase noise generated by an oscillator of a local receiver and/or a corresponding remote transmitter may cause the demodulator of the receiver to make incorrect decisions. Such incorrect decisions result in a higher bit error rate (BER), which may cause an unacceptable loss of information and reliability in a digital communication system.